Fractional distillation finds utility in the separation of many different chemical compounds in a variety of industries. The multiple stages of contacting and separation needed to perform this unit operation can be provided by a number of mechanical arrangements including packing and fractionation trays. When fractionation trays are employed a means must be provided to allow liquid to descend from tray to tray toward the bottom of the fractionation column countercurrent to rising vapor. In some tray designs a portion of the apparatus is dedicated to transporting the liquid downward. These designs typically employ a downcomer which delivers a stream of the liquid to the surface to the next lower tray. This stream may have a significant velocity and momentum which would allow the liquid to overcome the pressure of any vapor attempting to rise through the tray and a portion of the liquid would therefor tend to pass through any available opening where the descending liquid impacts the surface of the next lower tray. For this reason this area is in many instances imperforate and is referred to as the "receiving pan" of the tray.
One particular type of fractionation tray referred to in the art as a multiple downcomer tray does not have such imperforate receiving pans. In this tray design the descending liquid impacts directly upon the perforated surface of the vapor-liquid contacting area decking. This can lead to the undesired passage of liquid through the perforation and an undesired decrease in the tray's separation efficiency. A previously proposed solution to this problem is the provision of antipenetration pans between the liquid outlet at the bottom of the downcomer and the surface of the tray. These devices intercept the descending liquid and prevent the high velocity liquid from impacting onto the surface of the tray thus preventing the bypassing of liquid.